Nest thermostat 3rd generation not functioning correctly.

[PaulCousins]

Hi 

I have just hade my Utility room done and the kitchen fitter dissconected all the power sockets and The Nest Heat link to enable him to fit the back board splash back, seemed to know what he was doing as after he left I found a diagram he had made of the Heat link wires.

So putting the heating on last night it was all backwards when the heat link is in off mode with just one green neon light showing the central heating fires up and the thermostat and my phone app shows grey background and says off, then when you press the heat link again the central heating powers down and I have the three green neons displaying which normally is the display for the heating and water? at this point heating is off  and the the thermostat is showing orange with the temperature as if it’s on.

I am guessing one pair of wires are the wrong way round? I did a bit of digging around on the net and found an image of a Heat link with the grey wire in terminal 2 and the black wire in 3 and mine are the other way round black in 2 and grey in 3. I was going to swap these round thinking I had cracked it and had second thoughts as the grey and black are not designated to anything in particular like your brown is obviously live and blue neutral it might well have been wired like that originally so before swapping them was looking for advise, didn't want to swap them and short something.

[Frustratedddd · Accepted solution]

I assume from your information you have a Combi boiler?

I assume you have a live in L & a Neutral in N, correct?

I assume you have a wire in term 2 & term 3 correct?

The colours are not really helping, as any wire could be used.

Assuming that is correct and nothing else is connected, swap them round, they are switching the wrong way with the relay.

Always the best way in today's tech, take a picture of the wiring before you remove if in doubt!!!

[PaulCousins]

Hi 

yes you are correct it's a combi I swapped the wires over as you suggested but it was still the same so I swapped them back as they were but doing so noticed he had used 1 and 2 not 2and 3 despite his diagram he had done showed 2and 3 so once I put them back in 2 and 3 success, easy mistake to make I suppose.

It did cross my mind he had done it hoping I would ring him up and he would come round fix it and try to charge me but that's me being a bit  sinnicle, we all make mistakes myself included.

Thank you for your quick response to this much appreciated.

[Frustratedddd]

Easy mistake, but should have tested the system before leaving you!

The problem you had was a normally closed circuit, and should have been normally open circuit.

A point to check, make sure you have the live feed in term 2 not term 3. Still would work, but feed needs to be in term 2